You're going to share the jackpot with dozens of other winners, so it wouldn't be immediately obvious which of the winners rigged it. While if you pick a random number sequence and are the only winner, you'll be the prime suspect if anyone realises the draw was rigged.

As a prank and/or to expose how unsafe the system is.

Good point, I hadn't considered that. Seems pretty plausible.

-I'd say that is plausible if next week's draw turns out to be 1-2-3-4-5-6, for instance.

(That is - as is pointed out upthread, such 'weird' draws will occur naturally on occasion. It would, however, be quite suspicious if it happened twice in a row.)

I am sure one of the things the lottery looks into is how many coupons with 'weird' numbers chosen like this week's winning numbers have been picked in the past - of course, if you get a result which makes you suspect shenanigans AND the number of coupons with such a strange sequence of numbers is way up from normal, then perhaps that suspicion is well founded.

true ... might be an innocent mistake too.

mistake? As far as I can see, it could only be either intentional or the result of randomness.

It could also be an attempt to rig gone bad

Sure. I’d call that the result of an intentional action, but maybe that’s just personal preference.

There might be some error in the randomization process that caused consecutive balls to be drawn.

That’s a fair point. In that case it would be the result of a both a mistake and randomization.

software bugs are neither intentional not random